Problem: $\dfrac{3}{6} + \dfrac{3}{8} = {?}$
Answer: ${\dfrac{3}{6}}$ ${\dfrac{3}{8}}$ $+$ ${\dfrac{3 \times 4}{6 \times 4}}$ ${\dfrac{3 \times 3}{8 \times 3}}$ $+$ ${\dfrac{12}{24}}$ ${\dfrac{9}{24}}$ $+$ $ = \dfrac{{12} + {9}}{24} $ $ = \dfrac{21}{24}$